Apparatus for controlling one hydraulic pressure in accordance with another



Dec. 4, 1951 R. c. MOLEQD 2,577,027

APPARATUS FCR CONTROLLINC CNE HYDRAULIC PRESSURE IN ACCORDANCE WITH ANOTHER Filed oct. 50, 1911.5

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Patented Dec. 4, 1951 APPARATUS FOR CONTROLLING ONE HY- DRAULIC PRESSURE IN ACCORDANCE WITH ANOTHER Roderick Cristall McLeod, Cropston, England, assignor to Power Jets (Research & Development) Limited, London, England Application October 3i), 1945, Serial No. 625,568 In Great Britain February` 10, 1944 9 Claims. (Cl. 137-53) This invention relates to means whereby one hydraulic pressure is to be controlled in accordance with another; the Word hydraulic is used in its wider sense including gaseous pressures. The immediate application of the invention is to a fuel system of a specialised sort, namely that of the thrust augmenter of a jet propulsion system for aircraft. In this application certain characteristics are required of the fuel control,

and the invention, Whilst meeting the particular l requirement, will be seen to be capable of wider applications. l Broadly the invention enables one hydraulic pressure to be` controlled by another in accordance with the square of the second, or with modification, in other ratios or progressions. It can be foreseen thatin many applications, especially where restrictive orifices with quadratic characteristics are involved,'it may be desirable to be able to control hydraulic pressure in corresponding manner. n

The particular application of the invention, a statement of which will aid its clarification, is as follows. A propulsion system for aircraft comprises a prime mover consisting of a gas turbine driving a compressor in the output of which fuel is burned, the so-energised combustion products driving the turbine and then constituting a jet propulsion stream. To augment the thrust thus afforded, a second turbine is driven by this stream, and in turn drives a compressor or ducted fan which entrains new air and contributes it to the nal propulsive stream. In this new air, fuel (called secondary fuel) may be burned, still further augmenting the total thrust. The invention is concerned with the supply control of this secondary fuel, especially in the light of the combustion problem Which, as investigated experi- In order to secure efficient combustion in such a secondary stream without undue lcss of air pressure (such pressure loss having a very pronounced effect on thrust delivered) it is found desirable to use burner means which, for practical reasons such as simplicityand weight, are in technical effect simple orifices and thus have a pressure/flow characteristic substantially following a quadratic law. It is, moreover, desirable to interrelate the secondary fuel supply pressure With the pressure of supply of fuel to the prime mover, because thus any altitude compensation means provided for the prime mover, suffice also for the augmenter system (and other advantages of simplicity etc. are also afforded).

Thus the requirement emergesof controlling the supply pressure of the secondary fuel in accordance with the square of the pressure of the prime-mover fuel.

The invention provides apparatus which Will fulfill this requirement. Thus, according to the invention a piston or the like suogect to the pressure of one uid acts on a lever which in turn applies load to a valve controlling the pressure of a second fluid, and a second piston subJect also to the pressure of the first of the said fluids acts to vary the leverage ratio of the said lever as the pressure of the said first fluid varies. It will be clear that the effect of the first piston alone would be to vary the pressure of the second fluid proportionally to that of the rst. Clearly also the additional effect of the second piston is to vary the leverage ratio, so that if, for example, the variation is proportional to the pressure of the iirst of the said uids, the resultant effect will b'e that the load applied by the lever Will vary, in accordance with the square of the pressure of the second uid. Various other desired relationships could however be obtained. 1

One form of embodiment of the apparatus according to the invention will be describedby way -of example with reierence to the accompanying drawings in which:

Fig. 1 is a vertical section of said embodiment;`

Fig. 2 is a plan view in part section along the line A-B of Fig. 1 and Fig. 3 is an enlarged section along the line C-'D of Fig. 1.

Referring to the drawings, the fluid whose pressure is to be controlled is contained in a casing I and enters the apparatus by means of inlet I3. The pressure of this iiuid can be adjusted by a relief valve I I which is closable against the lower surface of the valve head 3'! and is provided with relief ports I2 through which the fluid to be controlled can flow to the fluid outlet 8 provided in the boss l.

The position of the valve head 3l' can be adjusted by its abutment against the nose 43 of a link lever 9 which is pivoted at a fulcrum I0 and on the upper surface I9 of which can roll a roller I5 mounted at one end of arod I6 so that the said rod can pivot about the extreme tip of its conical head I8 which bears pivotally against a conical centre 4 provided in a piston 6.

The roller I5 can rotate about its pivot 38 by means of ball bearings 3.

entry for the iluid exerting the controlling pres` sure which is consequently transmitted to the piston 6.

The casing I also comprises another extended tubular portion Iain Vwhich is heldv stationary' a sleeve 2 IWhich communicates with another inlet 42 for the fluid exerting the controlling pressure and over which can move a slidable hollow cylindrical piston 22. A spring l20 b ears atvonerend against an abutment 40 rigid with thecasing I and at its other end the said spring 20 bears against thrust washers 34 and ball bearings 21 the object of which is to preventfthe spring`2-0 from twisting when it is compressed. Thefassembly of spring 20, piston 22 and slee`ve"2l is held together by means of v,lock -nuts v52,3 andan external lock nut 26. One end of Lthe .pistonz22 is closed by a cap nut 25 adapted to engage on a suitably threaded part of said piston.

As seen more particularly in Fig. 3, the piston LV22 is 'connected "to links -35= by means` of Y pins-11I and is movable together Withfthelinks l*35 by means of trunnions '2 9' mounted on the ipivot 39.

-Theends of the links 35'are'rsecureditogether-by 'meansvof rivets A3 I.

The* inlets :39 `and--42 vfor the controlling uid Y-are connected hydraulically in'parallel, for example -by meansof a suitable pipe -M-and lthe lmode of operation ofthe-apparatus is as follows:

vThe controllingV pressure is' exerted throughthe 1Vinlet 39-on-tothe piston 6 which pressureis transmitted throughthemember'rl Efand the link lever-9 to thevalve head-3'I.

rIhe mechanical advantage of this leverlinkage is`varied'by the operationv of the controlling pressure-Which'is exerted also through the inlet i-II2 byu-id which enters sleeve 2I andexer-ts a thrust against the internal surface of the nut 25. `Wlhen this L-thrust' -exceeds V'the i force vexerted by spring-20which/acts-fso as to' tend to prevent the @piston- '22-from1 moving -to'fthe right asf-shown` in Fig. 1, the piston 22 ismoveditothe right Vcausing the links i3 51-to. move abymeans` of the -trunnions 29 and -thereby movngthe roller I5 over'the :surface I9 -of the! link-lever 9. The" eiect ofi the movement of roller I5 is to alterthe leverage-ex- -erted on the lvalve head 3 'I by -the controlling pressure iacting. through inlet 39--andthus to alter the mechanical advantage of the-adjusting Ameehanism.

By suitably adjusting the areas of thelheaId-of vpiston- 6 and valve :headS'I .and .the klengths of.` -the yvarious members .of .the lever.linkagerfbetween .piston 6 and valve head31, the variation the `pressure to be controlled can be arranged to have any desired relationship with the controlling pressure. Thus it will be seen'that the leverage ratio through which the Vpiston-"I5 Vapplies pres- --sure proportionally tothe fluid pressure` thereon to the valve head 3l can readily be madatovvary proportionally to the fluid pressure Aso-that `the Yload applied to the Valve head 31"Willvaryas= the square of that pressure.

Although in this particularexamplevthe.path

of the roller I5 is an arc I9 ofwa circle fof `:which `the centre is the tip of the conical lhead I-8,this

For example, the line of action ofthe.

4 shift the fulcrum I0 instead of the rod IG in cases where this may be preferable for mechanical or design reasons.

The valve II may if desired be replaced by a variable delivery pump or other suitable means deemed toinvolve themovement ofi alpart such as a valve, the abutment of a spring or an -equivalent. In this specification the term valve" ris intended-to include all such means. The term "/fpistolf'iv is alsoiinte'nded to include all equivalent means I claim:

)71. lrinoparatus Lfor I'controlling one hydraulic 4pressure in accordance with another comprising 'a'vaive "controlling the pressure to be controlled.

.a -pivotablymounted lever adapted to adjust said `vali/zafra member pivotably connected to a piston subject to the controlling pressure and adapted to"exe`rt"a turning moment on said lever about the pivot of said leverand a second piston subvject-to the controlling pressure-and adapted to vary -the said-turning moment.

2. Apparatus according to claim l'wliereinlfthe second pston'is Vadaptedto rotate said lmember about its-pivot.

f3. Apparatusv according-to claimll Lwherein the said member is adapted '-toimovablyl bear against the -saidlever.

f 4. Apparatus accordingsto claim 1w-herenf.the second piston is-adapted-toy rotatelsaifd member -aboutits pivot and Whereinfthef said imemberuis -adaptediv'to movably-'bear againstthe-.-said-lever.

y i'rlA-pparatus according to claim LWher-ei-nthe secondgpiston isadapted tomove the-pivotofl the said-lever.

6. Apparatus according-to claim .11 whereinlpivotally attached Ytoandf extending: 'laterally' fof ythe :general direction of 4said 4member is iazsifde1member connected Sito Vfthe :second fpiston.

'7. Apparatus according toclaimglwhereinthe Lsecond Kpistonlis adaptedfito rotate. sai'd fmexnber v:about itsipivot and wherein pivotally. attached? to and. extending.. laterally iofzthe...generala'dlreetion `of said membergis aisida-member-connecteditoathe second :piston v8. l Apparati-isi according; tol zclaim; 11 .whereinthe .said member-lisadaptedtomovably bear against the saidf flever-.Landwherein'pivotally. attached '-:to .and extending lateitllyvoi ther-general .direction .of said memberiisfaside member connected! tothe `second piston.

:'9. Apparatusfor control-lingpressure'Ioflafluid in accordancefwi-th a controlling;.pressureicom- ,prisingi a :valvecontrolling the? said .uida lever y Vlocatedztovbearfon andfload-A said valve; the pres- Asure of.- said fluid being `accordinglyLdeterrninedby the load thus'appled: to .the-valval azpistomsubject to `the `controlling pressure, `ccnnectedotozsaid lever to exertfa -turnngvmoment thereon; andna second: piston also :subject vto Vthewcontrolling pressure and lfa'dapted' to Avary the said turning moment v RODERICK CRISTALLI =MCLED.

REFERENCES `,GIED

'The following references :are of recordini the -le 4of thispatent:

UNITED STATES PATENTS l Number Name 1 Date `1,798,932 Dreiske vl r r r. MaraBl, 1931 2,396,911 .Anxionnaz V i Y -Mar .119,4946 

